To meet Federal Motor Vehicle Safety Standards, a vehicle may include an upper anchor attachment to receive a child safety seat tether hook connected to an upper portion of the child safety seat back. The connection of the upper portion of the child safety seat to the vehicle may reduce the forward movement of the child safety seat during a frontal crash. However, the shock applied by child safety seat restraining equipment to the child safety seat occupant may increase in the case of a forward vehicle collision.
One approach to reduce the impact of the collision force to the child safety seat is described in the U.S. Pat. No. 6,767,057. In particular, anchor attachments to the child safety seat with energy absorbing mechanisms are disclosed. In one example, the upper anchorage assembly includes a Z-shaped bracket having a first end that includes a longitudinally-arranged keyhole and slot with the keyhole positioned forward of the slot. A bolt extends through the keyhole and engages the vehicle structure. If a predetermined forward force is exceeded, then the fixed bolt deforms the bracket materials as it travels forward, enlarging the width of the slot. The deformation of the bracket along the slot absorbs energy.
However, the inventors herein have recognized disadvantages with such an energy absorbing device. Specifically, since the width of the slot is constant, the load applied to the child safety seat may be constant as the bracket travels forward, which may not be desired in some situations. Further, there may be a sudden impact on the child safety seat both when the bracket starts to travel along the slot and when the bolt hits the rearward end of the slot.